I have an image I am milling into a piece of wood stock. The stock is 3/8" thick. I would like to cut out this image from the square stock as a circle. Like a medallion that is 5.5 inches. I would like to mill out that perimeter the full 3/8" depth of the stock. I just can't figure out how to make that happen. The default stock is square and when I run that, it comes out nice. How do I make it nice but in a circle and not a square?